scholarly journals Dynamic Stress Drop of Recent Earthquakes: Variations within Subduction Zones

1999 ◽  
pp. 409-431
Author(s):  
Larry J. Ruff
Keyword(s):  
Stress Drop ◽  
Subduction Zones ◽  
Dynamic Stress ◽  
Dynamic Stress Drop ◽  
Recent Earthquakes

A dynamic model for far-field acceleration

1982 ◽  
Vol 72 (4) ◽  
pp. 1049-1068
Author(s):  
John Boatwright
Keyword(s):  
Stress Drop ◽  
High Frequency ◽  
Dynamic Stress ◽  
The Body ◽  
Body Waves ◽  
Far Field ◽  
Rupture Velocity ◽  
Frequency Level ◽  
Average Change ◽  
Dynamic Stress Drop

abstract A model for the far-field acceleration radiated by an incoherent rupture is constructed by combining Madariaga's (1977) theory for the high-frequency radiation from crack models of faulting with a simple statistical source model. By extending Madariaga's results to acceleration pulses with finite durations, the peak acceleration of a pulse radiated by a single stop or start of a crack tip is shown to depend on the dynamic stress drop of the subevent, the total change in rupture velocity, and the ratio of the subevent radius to the acceleration pulse width. An incoherent rupture is approximated by a sample from a self-similar distribution of coherent subevents. Assuming the subevents fit together without overlapping, the high-frequency level of the acceleration spectra depends linearly on the rms dynamic stress drop, the average change in rupture velocity, and the square root of the overall rupture area. The high-frequency level is independent, to first order, of the rupture complexity. Following Hanks (1979), simple approximations are derived for the relation between the rms dynamic stress drop and the rms acceleration, averaged over the pulse duration. This relation necessarily depends on the shape of the body-wave spectra. The body waves radiated by 10 small earthquakes near Monticello Dam, South Carolina, are analyzed to test these results. The average change of rupture velocity of Δv = 0.8β associated with the radiation of the acceleration pulses is estimated by comparing the rms acceleration contained in the P waves to that in the S waves. The rms dynamic stress drops of the 10 events, estimated from the rms accelerations, range from 0.4 to 1.9 bars and are strongly correlated with estimates of the apparent stress.

A Source Physics Interpretation of Nonself-Similar Double-Corner-Frequency Source Spectral Model JA19_2S

2022 ◽  
Author(s):  
Chen Ji ◽  
Ralph J. Archuleta
Keyword(s):  
Stress Drop ◽  
Wave Speed ◽  
Dynamic Stress ◽  
Corner Frequency ◽  
Rupture Velocity ◽  
Scaling Relation ◽  
Shear Wave Speed ◽  
Dynamic Stress Drop ◽  
Static Stress Drop ◽  
Frequency Source

Abstract We investigate the relation between the kinematic double-corner-frequency source spectral model JA19_2S (Ji and Archuleta, 2020) and static fault geometry scaling relations proposed by Leonard (2010). We find that the nonself-similar low-corner-frequency scaling relation of JA19_2S model can be explained using the fault length scaling relation of Leonard’s model combined with an average rupture velocity ∼70% of shear-wave speed for earthquakes 5.3 < M< 6.9. Earthquakes consistent with both models have magnitude-independent average static stress drop and average dynamic stress drop around 3 MPa. Their scaled energy e˜ is not a constant. The decrease of e˜ with magnitude can be fully explained by the magnitude dependence of the fault aspect ratio. The high-frequency source radiation is generally controlled by seismic moment, static stress drop, and dynamic stress drop but is further modulated by the fault aspect ratio and the relative location of the hypocenter. Based on these two models, the commonly quoted average rupture velocity of 70%–80% of shear-wave speed implies predominantly unilateral rupture.

Source physics interpretation of non-self-similar double-corner frequency source spectral model JA19_2S

2021 ◽  
Author(s):  
Chen Ji ◽  
Ralph Archuleta
Keyword(s):  
Aspect Ratio ◽  
Stress Drop ◽  
Dynamic Stress ◽  
Static Stress ◽  
Corner Frequency ◽  
Rupture Velocity ◽  
Dynamic Stress Drop ◽  
Self Similar ◽  
Static Stress Drop ◽  
Frequency Source

<p>Source spectral models developed for strong ground motion simulations are phenomenological models that represent the average effect that the source processes have on near fault ground motion. Their parameters are directly regressed from the observations and often do not have clear meaning for the physics of the source process. We investigate the relation between the kinematic double-corner frequency (DCF) source spectral model JA19_2S (Ji and Archuleta, BSSA, 2020) and static fault geometry scaling relations proposed by Leonard (2010). We derive scaling relations for the low and high corner frequency in terms of static stress drop, dynamic stress drop, fault rupture velocity, fault aspect ratio, and relative hypocenter location. We find that the non-self-similar low corner frequency  scaling relation of JA19_2S model for 5.3<<strong>M</strong><6.9 earthquakes is well explained using the fault length scaling relation of Leonard’s model combined with a constant rupture velocity. Earthquakes following both models have constant average static stress drop and constant average dynamic stress drop. The high frequency source radiation is controlled by seismic moment, static stress drop and dynamic stress drop but strongly modulated by the fault aspect ratio and the hypocenter’s relative location. The mean, scaled energy  (or apparent stress) decreases with magnitude due to the magnitude dependence of the fault aspect ratio. Based on these two models, the commonly quoted average rupture velocity of 70-80% of shear wave speed implies predominantly unilateral rupture.</p>

Earthquake triggering of mud volcanoes and fluid seepage systems in fold-and-thrust belts and subduction zones

2020 ◽  
Author(s):  
Marco Bonini ◽  
Daniele Maestrelli
Keyword(s):  
Subduction Zones ◽  
Dynamic Stress ◽  
Static Stress ◽  
Mud Volcanoes ◽  
Dynamic Stresses ◽  
Thrust Belts ◽  
Stress Changes ◽  
Fold And Thrust Belts ◽  
Recent Earthquakes

<p>Various types of fluid expulsion features occur often at fold-and-thrust belts and subduction zones. The seepage features originate from the discharge and extrusion to the topographic surface of fluids, gases and possibly solid material, which are sourced from in-depth reservoirs. Earthquakes can occasionally trigger the eruption or increased activity of mud volcanoes and other seepage systems. The role of static and dynamic stress changes in the triggering will vary depending on the position of the seepage features with respect to the earthquake source fault. When the seepage system is controlled by faults that rupture and generate earthquakes, the role of static stress changes is likely to be influential. Subduction zones have the highest seismic potential on Earth, so large subduction earthquakes can stress massively the fault-controlled feeder systems of seepage features located above subduction thrusts. The potential role of coseismic static stress loading on fluid expulsion systems has been evaluated for accretionary and erosional subduction margins. The most significant effects occur in the epicentral area where subduction earthquakes can produce coseismic normal stress changes exceeding 20-40 bar, although these are generally restricted to relatively small regions. The magnitude of such stress changes may exceed the tensile strength of many rock anisotropies and increase crustal permeability by dilating fault-controlled conduits channeling fluids upwards. Also in fold-and-thrust belts seepage features may be associated with seismogenic faults. For instance, rupture of the Chihshang Fault (Taiwan) in 2003 produced the Mw6.8 Chengkung earthquake, which unclamped by 3 bar the feeder system of the nearby mud volcanoes that erupted shortly after the earthquake. A similar setting is also inferred for the seismogenic Pede-Apennine thrust system in northern Italy, which is also structurally controlling a number of mud volcanoes located on its hangingwall.</p><p>Seepage features can be often trigged off by dynamic stress changes created by earthquake faults located in the intermediate- to far-field. Peak dynamic stresses related to historical and recent earthquakes that produced a response of seepage systems in the Northern Apennines fold-and-thrust belt (Italy) are calculated through PGV (measured or evaluated through GMPEs). We document response of seepage systems to some historical and recent earthquakes. Some methane vents and springs showed paroxysmal activity that was influenced by peak dynamic stress of 0.3-0.4 bar, while mud volcanoes apparently showed lower sensitivity, being influenced by dynamic stresses with amplitude ranging between 0.5 and 3.5 bar. Recently, 17 mud volcanoes erupted shortly after the main seismic events of the 2016 Central Italy seismic sequence (Mwmax6.5), showing a clear correlation with peak dynamic stresses of the order of 2-4 bar (static stress changes are instead negligible or negative).</p><p>These results collectively suggest that seepage features may respond in different ways to dynamic and static stresses depending on earthquake magnitude and epicentral distances, and that they may show different sensitivity to stress changes. Dynamic stresses are likely to exert the dominant control on the triggering, even though static stress changes can also significantly influence seepage features in the near-field.</p>

Predicted near-field ground motion for dynamic stress-drop models

1985 ◽  
Vol 123 (2) ◽  
pp. 173-198 ◽  
Author(s):  
C -I. Trifu ◽  
M. Radulian
Keyword(s):  
Ground Motion ◽  
Stress Drop ◽  
Dynamic Stress ◽  
Near Field ◽  
Dynamic Stress Drop

Broadband analysis of the extended foreshock sequence of the Miyagi-Oki earthquake of 12 June 1978

1982 ◽  
Vol 72 (6A) ◽  
pp. 2017-2036
Author(s):  
George L. Choy ◽  
John Boatwright
Keyword(s):  
Stress Drop ◽  
Dynamic Stress ◽  
Main Shock ◽  
Body Waves ◽  
The Third ◽  
Radiated Energy ◽  
Dynamic Stress Drop ◽  
Static Stress Drop ◽  
Stress Drops ◽  
Seismograph Network

abstract The Miyagi-Oki earthquake of 12 June 1978, a large (Ms 7.8) interplate thrust event, occurred in a region which had not experienced earthquakes of magnitude greater than 7 since 1938. A sequence of four moderate-sized (5.4 < mb < 6.1) earthquakes encircled the rupture zone of the Miyagi-Oki earthquake over a period of 2 yr before the main shock. Broadband displacement and velocity records of body waves recorded digitally by stations of the Global Digital Seismograph Network are analyzed to determine the static and dynamic characteristics of the sequence. These characteristics include moment, radiated energy, dynamic and static stress drop, and apparent stress. Inversions of duration measurements made on the velocity waveforms permit quantifying the complexity of an event as well as constraining its rupture geometry. Intervals of 7 to 8 months separated the first three events; the main shock occurred 4 months after the third event. The rupture process of the third event was relatively complex; the event also had a substantially higher dynamic stress drop (175 bars) than did the stress drops of the first two events (9 and 10 bars, respectively). These observations suggest that the third event was an interme-diate-term precursor to the main shock. The fourth event, a short-term precursor to the main shock, occurred about 8 min before the main shock. Its dynamic stress drop (20 bars) was lower than that of the third event but higher than that of the first two events.

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